The invention relates to a method for the treatment of air, in particular for pneumatic brake systems of utility vehicles, having the steps of feeding compressed air to a compressed air storage tank through an air dryer, initiating a regeneration of the air dryer by virtue of regeneration air from the compressed air storage tank being conducted through the air dryer and discharged from there via a discharge valve, and calculating the theoretically required regeneration air quantity QReg,th.
The invention also relates to an air treatment system for pneumatic brake systems of utility vehicles, having a compressed air source, an air dryer, a compressed air tank, a discharge valve and a regeneration valve.
Air treatment systems of the generic type serve to supply treated, that is to say in particular dried, compressed air to the brake system and other compressed air consumers of utility or commercial vehicles. The drying of the compressed air which is supplied by a compressor takes place in a dryer cartridge of an air filter. Since water remains in the dryer cartridge on account of the dehumidification of the air, it is necessary to regenerate said dryer cartridge from time to time. For this purpose, a discharge valve which is arranged between the compressor and the dryer unit is opened, and it is made possible by using other suitable valve switching processes for compressed air to flow from a compressed air storage tank, which was filled previously by the compressor, through the dryer unit in the reverse direction in order to then be discharged into the atmosphere through the discharge valve.
Since no compressed air can be fed into the tank during the regeneration, it is sought to keep the regeneration phases as short as possible. On the other hand, it is however also important not to end the regeneration too early, in order that sufficient drying of the filter unit can ultimately take place. It is therefore sought overall to conduct the optimum compressed air quantity through the dryer unit for the purpose of regeneration.
German Patent Documents DE 199 11 741 A1 and DE 34 45 699 A1 are concerned with said problem.
In DE 199 11 741 A1, the required regeneration time is determined on a theoretical basis. The method is therefore based on permanently input parameters of the compressor which vary over the service life of the compressor and of the compressed air supply system. It is therefore conceivable that an excessive accumulation of moisture in the air treatment system and therefore also in the connected brake system will not be detected early.
DE 34 45 699 A1 specifies a method which is based on a humidity regulating circuit. The method is therefore based on the measurement variable of a sensor which can drift over the course of its service life, for example as a result of contamination. There is therefore the risk of an excess accumulation of water in the systems in the case of said system too.
The exemplary embodiments of the invention are based on specifying a method and an air treatment system which ensure the selection of an optimum regeneration air quantity and reduce the risk of an excess accumulation of water in the system.
The invention improves on the generic method for example, in that the presence of condensate in a region downstream of the air dryer is detected, in that, in the absence of condensate, a regeneration is carried out with the theoretically required regeneration air quantity QReg,th, and in that, in the presence of condensate, a regeneration is carried out with a corrected required regeneration air quantity QReg,corr, with the corrected required regeneration air quantity QReg,corr being greater than the theoretically required regeneration air quantity QReg,th. A base quantity of the required regeneration air is therefore calculated theoretically on the basis of the method according to the invention. Said base quantity should generally be sufficient for regeneration and the regeneration phase should not extend beyond those values. If it is however detected that condensate is present downstream of the air dryer, then it is to be assumed that the theoretically calculated regeneration air quantity is possibly insufficient. Use is consequently made of a corrected regeneration air quantity which is greater than the calculated base quantity.
In the simplest case, it is provided that the regeneration air quantities QReg are determined by setting the regeneration durations tReg. Under normal circumstances, the regeneration air quantity is related to the regeneration duration in a virtually linear relationship.
According to one preferred embodiment of the invention, it is provided that the presence of condensate in a condensate collecting tank in the region of the compressed air storage tank is detected. A condensate sensor can then be provided in a condensate collecting tank of said type, which condensate sensor is, in the simplest case, embodied as a switch. Said switch is actuated in the case of condensate being present, so that a corresponding signal is provided for a controller.
It can likewise be preferable that, in the presence of condensate, a regeneration is carried out with a corrected required regeneration duration tReg,corr when the condensate quantity exceeds a predefined threshold value. It is accordingly possible, depending on the configuration of the method according to the invention, to permit a certain precipitated condensate quantity and to nevertheless operate with the theoretically calculated regeneration air quantity QReg,th.
It can also be provided that the corrected required regeneration duration tReg,corr is greater by a predefined time interval than the theoretically required regeneration duration tReg,th. This is a simple possibility for defining the corrected required regeneration duration tReg,corr as a function of the theoretical regeneration duration tReg,th.
According to a further embodiment of the invention, it is provided that the corrected required regeneration duration tReg,corr is calculated by multiplication of the theoretically required regeneration duration tReg,th. In this way, it is obtained the corrected regeneration duration tReg,corr is defined in relation to the theoretical regeneration duration tReg,th.
The invention improves on the generic air treatment system in that a condensate sensor is arranged in the region downstream of the air dryer. In this way, the advantages and peculiarities of the method according to the invention are also realized within the context of an air treatment system.
The air treatment system is in particular provided for carrying out a method according to the invention.
The invention is now explained by way of example with reference to the appended drawings on the basis of particularly preferred embodiments.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.